All manner and variety of absorbent articles configured for the absorption of body fluids such as menses, urine, and feces are, of course, well known. Absorbent articles are typically comprised of a number of layers of material. These generally include, from top to bottom, a liquid pervious layer, an absorbent layer, and a liquid impervious layer. Additional layers may also be interposed between any of these layers. Such additional layers may serve various different purposes.
The layers of absorbent articles are generally held together around their peripheries by some conventional means, such as adhesives, crimping, fusing, and other methods known in the art. The absorbent articles can have, and in many cases preferably will have, a liquid impermeable bond around their periphery. This will not interfere with the function of the absorbent article. However, it is frequently also desirable to bond the layers together at their faces. The attachment of the faces of these layers presents certain technical problems. This is particularly the case when it is desired to attach the upper liquid pervious layers and absorbent layers. The same means used for attaching the layers at their peripheries often cannot be used because they will tend to block the flow of liquids to the absorbent layers.
A number of attempts have been made to deal with this problem. These have included utilizing hot melt adhesives, and other non-water based adhesives. Such adhesives will be less likely to dissolve when contacted by body liquids. Other attempts have been directed at applying adhesives in very thin layers or in particular patterns to attempt to minimize the interference with the flow of liquids to the underlying layers. U.S. Pat. No. 4,573,986 issued to Minetola, et al. on Mar. 4, 1986 discloses one preferred way of applying adhesives. Although the application of adhesives in the manner described in the Minetola, et al. patent works quite well, the search for improved ways of securing the faces of the layers of absorbent products has continued.
The main reason for searching for improved ways of securing the faces of such layers is that in many cases, adhesives which initially function adequately, may eventually fail and cause the liquid pervious layers to become unattached. This problem is particularly apparent during prolonged use of an absorbent article. This problem is often heightened when the liquid pervious layer is an apertured plastic film. While apertured plastic films made according to the patents owned by the assignee of the present invention perform very well, certain problems can occur when they separate from their underlying layers. The plastic films are sufficiently thin that they can move well into the crevices of the wearer's body (such as the space between the wearer's buttocks) when they become unattached. This can be extremely uncomfortable and irritating. Because of its plastic composition, in some of these instances, the liquid pervious layer may even stick to the skin of the wearer. The adhesives may cause the film to present a sticky surface near the body of the wearer which may contribute to cause the liquid pervious layer to stick to the skin of the wearer.
The separation of the apertured film from the absorbent layers may also cause exudates to run off the top of the product along the longitudinal edges. Further, the exudates will not always penetrate the film if there is no longer an underlying absorbent layer in contact with the film for the exudates to wick into. This is particularly true in the case of thick pads having airfelt batts for their absorbent cores. The absorbent core of such thick pads tends to collapse and bunch (or gather in transversely) in the center of the product upon the first incidence of wetting. This gathering in, combined with the separation of the formed film, leaves the portion of the pad adjacent to its longitudinal edges without any underlying absorbent material, thereby increasing the possibility of runoff or leakage on top of the product along the longitudinal edges.
Several patents describe absorbent products having layers held together in alternative manners for various different purposes. Such efforts are described in U.S. Pat. Nos. 3,965,906 and 4,184,902 issued to Karami, U.S. Pat. No. 4,391,861 issued to Butterworth, et al., U.S. Pat. No. 4,397,644 issued to Matthews, et al., U.S. Pat. No. 4,475,911 issued to Gellert, U.S. Pat. No. 4,726,976 issued to Karami, et al., U.S. Pat. No. 4,752,349 issued to Gebel, U.S. Pat. No. 4,753,840 issued to Van Gompel, U.S. Pat. No. 4,823,783 issued to Willhite, Jr., et al., U.S. Pat. No. 4,844,965 issued to Foxman, and U.S. Pat. No. 4,908,026 issued to Sukiennik, et al. The majority of these patents, however, do not disclose fusing an apertured formed film on top of a liquid pervious material or an absorbent material, such as a nonwoven material. Such patents also do not disclose providing an absorbent article with an unbonded window on its body-facing side for improved acquisition.
Thus, a need exists for absorbent articles having improved bonding between their layers, particularly between the uppermost liquid pervious layers.
Therefore, it is an object of the present invention to provide absorbent articles having bonding between their layers, particularly the uppermost liquid pervious layers, that maintain sustained attachment even under prolonged use and are provided with more controlled resistance to undesirable bunching.
It is another object of the present invention to provide absorbent articles having liquid pervious layers that are bonded in a manner that does not interfere with the acquisition of liquids into the absorbent layer.
These and other objects of the present invention will be more readily apparent when considered in reference to the following description and when taken in conjunction with the accompanying drawings.